The purpose of this project is to study the cell biology of various parasites in relation to the organism itself, its interaction with the host cell and production of disease. Current areas of interest are: 1) development of immunity; 2) effect of drugs on the parasite life cycle; 3) comparative ultra structure of infective forms (sporozoites) of related parasites; and 4) asexual and sexual development of the parasite. Emphasis is placed on Toxoplasma gondii and toxoplasmosis with members of the genera Hammondia, Sarcocystis and Isospora being used for comparative purposes. Techniques used include electron microscopy, tissure culture, serology and animal infections.